This invention relates to an apparatus for controlling the injection of fuel in an internal combustion engine, such as a diesel engine.
It is necessary to control the initiation of injection of fuel in accordance with various engine conditions, such as the rate of rotation and the temperature of the engine, or atmospheric parameters, such as the atmospheric temperature, so as to obtain an optimum engine performance. There is known a pressure-operated fuel injection control (advance) apparatus which operates in response to electrical signals from sensors which are known per se and which detect various parameters, such as the engine temperature or the number of revolutions, as mentioned above. The pressure-operated fuel injection control apparatus is connected to a pressure source. Usually, the pressure source is an oil delivery pump or a vacuum pump.
There are two types of oil pumps or vacuum pumps: the engine-driven type and the electrical motor-driven type. In an engine-driven pump driven by an internal combustion engine, the pump cannot produce a pressure sufficient to actuate the fuel injection advance apparatus when the engine is started, so that fuel injection cannot be advanced. However, it is necessary, as is well known, to advance the fuel injection when the engine is started since the engine temperature is low and since the combustion rate of the fuel tends to decrease.
On the other hand, this problem can be solved by a motor-driven pump. However, in the case of a motor-driven pump, a motor and a pump which is driven by the motor, which are not usually provided in an automobile, must be additionally provided. Furthermore, a motor-driven pump is usually rather expensive in comparison with an engine-driven pump.